Detection of plastic deformation in structural steel using scanning SQUID microscopy

The magneto- mechanical behaviour of structural steel specimens stressed up to a plastic deformation stage using a high- Tc scanning SQUID ( superconducting quantum interference device) microscope is investigated. The correlation between the gradient of the normal component of the magnetization and dislocation density, before the crack initiation, is carried out. The capability of scanning SQUID microscopy to detect the residual magnetization, due to the tensile stress, with a non- invasive technique is reported.